Production of chlorine and sodium sulphate

Abstract

A process for the preparation of chlorine and sodium sulphate which contains the steps of reacting sulphuric acid with sodium sulphate and ferric oxide or alumina, crystallizing and drying the resulting double salt trisodium-iron(III) sulphate or trisodium-aluminum sulphate and roasting the obtained trisodium-iron(III) sulphate or trisodium-aluminum sulphate with sodium chloride under the influence of oxygen thereby forming sodium sulphate, chlorine and ferric oxide or alumina.

What is claimed is: 
     
       1. A process for the preparation of chlorine and sodium sulphate which comprises reacting sulphuric acid with sodium sulphate and ferric oxide or alumina, crystallizing and drying the resulting double salt trisodium-iron(III) sulphate or trisodium-aluminum sulphate and roasting the obtained trisodium-iron(III) sulphate or trisodium-aluminum sulphate with sodium chloride under the influence of oxygen thereby forming sodium sulphate, chlorine and ferric oxide or alumina. 
     
     
       2. A process according to claim 1, wherein the drying of trisodium-iron (III) sulphate is carried out at a temperature greater than 300° C. 
     
     
       3. The process according to claim 2, wherein the drying of trisodium-iron(III) sulphate is carried out at a temperature between 300° C. and 450° C. 
     
     
       4. The process according to claim 1 or 2, wherein the sulphuric acid is spent sulphuric acid in an aqueous medium. 
     
     
       5. The process according to claim 1, wherein the molar ratios of H 2  SO 4  : Na 2  SO 4  : Fe 2  O 3  are about 3:3:1. 
     
     
       6. The process according to claim 1, wherein the roasting is carried out at a temperature between 450° C. and 800° C. 
     
     
       7. The process according to claim 6, wherein the roasting temperature is between 470° C. and 580° C. 
     
     
       8. The process according to claim 7, wherein the roasting reaction is performed in a mechanical kiln. 
     
     
       9. The process according to claims 1, 2, 7 or 8 wherein sodium sulphate and/or ferric oxide, obtained by the roasting step, is recycled to react with the sulphuric acid. 
     
     
       10. The process according to claim 9, wherein a part of the ferric oxide is recycled to react with the sulphuric acid and a part is removed. 
     
     
       11. The process according to claims 1, 2 or 7, wherein a part of the product of the roasting reaction is purified by reaction with a base. 
     
     
       12. The process according to claim 11, wherein the purified sodium sulphate product is further reacted with a base and magnesium impurity is removed as magnesium hydroxide. 
     
     
       13. The process according to claim 12, wherein sodium sulphate is crystallized and separated from the base-treated product of the roasting reaction. 
     
     
       14. A process for the preparation of chlorine and sodium sulphate which comprises reacting spent sulphuric acid with sodium sulphate and ferric oxide or alumina, crystallizing and drying the resulting double salt trisodium-iron(III) sulphate or trisodium-aluminum sulphate and roasting the obtained trisodium-iron(III) sulphate or trisodium-aluminum sulphate with sodium chloride under the influence of oxygen thereby forming sodium sulphate, chloride and ferric oxide or alumina wherein the spent sulphuric acid contains main impurities of Fe, Al, and Mg in the sulphate form and the crude sodium sulphate contains main impurities of ferric oxide, alumina, and magnesium sulphate; spent sulphuric acid and crude sodium sulphate are mixed at about 50° to 100° C. and the product is then dried in a mechanical rotary kiln at about 300° to 450° C. under introduction of air; the product is then mixed with ground sodium chloride and roasted in a rotary kiln at about 470° to 580° C.